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Meet – and hear – the world’s first bilingual chimps

By Andy Coghlan

Apple’s the word. Chimpanzees can learn to grunt “apple” in two chimp languages – a finding that questions how unique our own language abilities are.

Researchers have kept records of vocalisations of a group of adult chimps from the Netherlands before and after the move to Edinburgh zoo. Three years later, recordings show, the Dutch chimps had picked up the pronunciation of their Scottish hosts.

Video: Chimp changes its grunts after move to Scotland

The finding challenges the prevailing theory that chimp words for objects are fixed because they result from excited, involuntary outbursts. Humans can easily learn foreign words that refer to a specific object, and it was assumed that chimps and other animals could not, perhaps owing to their different brain structure. This has long been argued to be one of the talents making humans unique.

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The assumption has been that animals do not have control over the sounds they make, whereas we socially learn the labels for things – which is what separates us from animals, says Katie Slocombe of the University of York, UK.

But this may be wrong, it seems. “The important thing we’ve now shown is that with the food calls, they changed the structure to fit in with their new group members, so the Dutch calls for ‘apple’ changed to the Edinburgh ones,” says Slocombe. “It’s the first time call structure has been dissociated from emotional outbursts.”

Learning the lingo

Slocombe’s team recorded apple calls from six “local” and seven “immigrant” chimps in 2010, before they were united in 2012 and 2013. Then they analysed the acoustics of the calls. They choose to analyse calls for “apple” because this was the most different call between the groups.

The Dutch calls gradually changed to match the local argot in the second year, when the two groups had completely intermingled and formed strong friendships with each other. This means that like us, chimps can learn foreign lingo to fit in with new neighbours.

The peak frequencies of Dutch chimps’ calls dropped dramatically from 932 to 708 hertz between 2010 and 2013, matching closely the calls of the Scottish group, which altered slightly from 657 to 597 hertz over the same period. This made the Dutch grunts less shrill and much closer to the low-toned grunts of the native chimps (see video above).

It is feasible that chimps can learn new words in the wild, too, says Slocombe. Female but not male chimps in neighbouring communities sometimes swap groups, and Slocombe says it would be fascinating to find out whether they alter their calls. “It makes sense, if you change groups, trying to fit in by making the same calls, but we need to show it happens,” she says.

Ancient origins

Perhaps a larger implication is that the ability to learn new words for the same object may extend way beyond humans, even back 6 million years to the last common ancestor of humans and apes before they went their separate ways. “We would infer that they had some flexibility to learn social labels,” she says.

“This is a very exciting discovery,” says Andy Whiten of the University of St Andrews in Scotland, whose own work has shown that chimps can learn to use tools by copying others. “Different communities have different material cultures in the wild, but their vocal communication has always been thought to be more fixed,” he says. “This new research suggests that can vary culturally too, as it does in humans.”

Not everyone is convinced, though. “It adds to evidence primate vocal communication is more plastic than traditionally thought, but I’m sceptical that it calls into question the idea that these calls have a largely emotional basis,” says Brandon Wheeler of the University of Kent in Canterbury, UK. “Like [human] laughter, chimp food-associated grunts are species-specific calls that vary modestly based on what we might call ‘learned’ accents, but this is rather different from the fact that the Spanish use the word ‘manzana’ to refer to what the English call ‘apples’.”